A rotary stone-cutting head normally has a body generally centered on and adapted to be rotated in a predetermined direction about a normally upright axis. One axial face, normally the bottom face, of this body has a plurality of teeth having cutting edges that are directed angularly generally forwardly in a predetermined direction of rotation of the body about its axis. A suction arrangement opens at the normally open center of the body so that chips and so on freed by the teeth are carried off, normally along with water or another liquid fed to the tool to lubricate and cool it as well as to serve as a vehicle for the freed chips.
These cutting edges therefore do virtually all of the removal work. Hence they get quite hot and are subjected to enormous wear. Thus it is standard practice to form these teeth of separate hardened-steel elements that are secured to the face of the drilling or cutting head. Appropriately edges small hardened-steel plates are therefore brazed or soldered to appropriate seats on the front or lower body face.
The main problem with this system is that the heat generated by the heavy-duty cutting and scraping at the cutting edges weakens the bond between the edge-forming elements and their supports. Hence these elements come loose and fall off, exposing the softer underlying metal--normally cast iron--to abrasion. Another problem is that the body surface normally erodes greatly around each such harder edge-forming element, so the body eventually becomes unusable.